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A clarification on Nano-T

Alvin T. Grey

Well lookie what I found here..

(open PDF, the link is included, I'll quote a partial referecnce)

*note CMNH 7541 is Nano-T

http://www.oucom.ohiou.edu/dbms-witmer/Downloads/2009_Witmer_&_Ridgely_tyrannosaur_brains_&_ears.pdf

It is indeed frustrating that one of the only skeletal
elements that is missing from the beautifully preserved
BMR P2002.4.1 is, in fact, the braincase. Given the
obvious closeness of CMNH 7541 and BMR P2002.4.1, it
would likely have been taxonomically decisive. Our data
on CMNH 7541 may be taken as evidence for the validity
of N. lancensis on the grounds that it is ‘‘too different’’
from T. rex. However, we are hesitant to argue that
the debate over its status is settled for the simple reason
of sample size. CMNH 7541 presents one specimen—one
highly divergent specimen. Although we see no clear
signs of distortion or pathology in the braincase, its divergent
nature concerns us, and we maintain that the
possibility remains that future discoveries will show
CMNH 7541 to be aberrant. For that reason, we urge
caution and continue to regard the specimen’s status as
open.

To save you some reading, basically, Nano-T had a whole lot of differences when compared to other Tyranosaurids. The seemed to be way more basal. The animal was not all that young. However it is known from only one fossil for certain, and that is why the question remains open. So, was Nano-T a different species? - Or was it a hidiously disfigured mutant dino that the others pointed at and/or shooed their kids away from? I'm going with 'Different' even if it means that we now have that hated of all headlines:

Another T-Rex Relative Discovered!!!!

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Galvasean

Nano-T, I like it!
I look forward to reading the paper in full later. Oh how I would love for Nanotyrannus to be proved valid, if only to ad it to the list of things Jack Horner got wrong :P

Adam Khor

I wish Nanotyrannus is its own genus or at least species... as fascinating as the idea of T-Rex having the monopoly over the giant predator niche in the latest Cretaceous of NA, it is always more interesting to have several of them... makes more sense, too, IMO, as long as they were adapted to hunt for different prey.

Alvin T. Grey

Adam Khor wrote: »

I wish Nanotyrannus is its own genus or at least species... as fascinating as the idea of T-Rex having the monopoly over the giant predator niche in the latest Cretaceous of NA, it is always more interesting to have several of them... makes more sense, too, IMO, as long as they were adapted to hunt for different prey.

It's a good bet their prey was different. If they are a different species (which in my opinion they are) then the teeth they had were the teeth they kept. One of the JH opinions is that the number of teeth, and the shape of teeth changed from juvenile T-Rex to adult, and hence Nano-T was a juvenile Rex. And the reason for the change in teeth was different prey items and hunting methods as the animal matured.

So if we agree with the premise that different dentation indicates different predation, then if Nano-T is a different species, it follows that Nano-T hunted different animals.

What is not being considered by Mr. H. is that many believe that Rex's hunted in packs. If that is true then they shared in the same kill.
We know that Allosaurs and Albertasaurs did. We think that daspletasaurs did, so it follows that Rex's may have.

If they shared the same kill, then they must have eaten the same kill.
If they ate that same animal, then their teeth need to be the same in order to do the job. Thank you Mr. darwin's finches.....

So if you agree with the above (based on sound principals that have been tested) Then what the Juvenile Rex theory seems to imply is that juvenile Rexs did not hunt with adults, or did not hunt the same prey.

In nature that is a wayyyyy too complicated solution.

Adam Khor

Alvin T. Grey wrote: »

It's a good bet their prey was different. If they are a different species (which in my opinion they are) then the teeth they had were the teeth they kept. One of the JH opinions is that the number of teeth, and the shape of teeth changed from juvenile T-Rex to adult, and hence Nano-T was a juvenile Rex. And the reason for the change in teeth was different prey items and hunting methods as the animal matured.

So if we agree with the premise that different dentation indicates different predation, then if Nano-T is a different species, it follows that Nano-T hunted different animals.

What is not being considered by Mr. H. is that many believe that Rex's hunted in packs. If that is true then they shared in the same kill.
We know that Allosaurs and Albertasaurs did. We think that daspletasaurs did, so it follows that Rex's may have.

If they shared the same kill, then they must have eaten the same kill.
If they ate that same animal, then their teeth need to be the same in order to do the job. Thank you Mr. darwin's finches.....

So if you agree with the above (based on sound principals that have been tested) Then what the Juvenile Rex theory seems to imply is that juvenile Rexs did not hunt with adults, or did not hunt the same prey.

In nature that is a wayyyyy too complicated solution.

Hmmm... I'm gonna have to disagree here. For starters, although Allosaurs and Albertosaurs have been found in groups, this doesn`t prove that they were hunting together. Komodo dragons are lone hunters, but they gather together to feed when there is a large carcass available. The young Komodos usually wait until the big ones finish their meal, but they still roam near waiting for their chance, so I can imagine a group of say, albertosaurs gathering together like this, attracted by the stench of a dead animal (or the smell of blood from a recent kill) and feasting together. You would find juveniles like in Komodo dragon gatherings without it meaning that they were part of a family group or "pack".

As for juvenile T-Rex not feeding on the same prey than adults, I don`t see why this should be strange. Adult crocodiles can feed on buffalo, zebra, you name it, but juveniles feed on fish and smaller animals simply because that's what they can capture. Same goes with sharks. I don`t think there is any hard evidence saying that juvenile T-Rex stayed with their parents and were raised and fed like (most) birds and mammals are today.
They could very well live separately (the juveniles probably forming small groups to protect themselves against predators, just like young crocodiles and some sharks do) and hunt small prey by themselves.
There's actually some evidence that certain herbivorous dinos such as Triceratops and some ornithomimids formed groups when they weren`t yet fully grown; kinda like teenager gangs, to protect themselves better against predators.
Since T-Rex is known to have been cannibalistic, it shouldn`t be surprising if young tyrannosaurs did the same. IMHO, anyways.

Alvin T. Grey

Adam Khor wrote: »

Hmmm... I'm gonna have to disagree here. For starters, although Allosaurs and Albertosaurs have been found in groups, this doesn`t prove that they were hunting together. Komodo dragons are lone hunters, but they gather together to feed when there is a large carcass available. The young Komodos usually wait until the big ones finish their meal, but they still roam near waiting for their chance, so I can imagine a group of say, albertosaurs gathering together like this, attracted by the stench of a dead animal (or the smell of blood from a recent kill) and feasting together. You would find juveniles like in Komodo dragon gatherings without it meaning that they were part of a family group or "pack".

As for juvenile T-Rex not feeding on the same prey than adults, I don`t see why this should be strange. Adult crocodiles can feed on buffalo, zebra, you name it, but juveniles feed on fish and smaller animals simply because that's what they can capture. Same goes with sharks. I don`t think there is any hard evidence saying that juvenile T-Rex stayed with their parents and were raised and fed like (most) birds and mammals are today.
They could very well live separately (the juveniles probably forming small groups to protect themselves against predators, just like young crocodiles and some sharks do) and hunt small prey by themselves.
There's actually some evidence that certain herbivorous dinos such as Triceratops and some ornithomimids formed groups when they weren`t yet fully grown; kinda like teenager gangs, to protect themselves better against predators.
Since T-Rex is known to have been cannibalistic, it shouldn`t be surprising if young tyrannosaurs did the same. IMHO, anyways.

Sorry Adam if this seems a little short, but it's busy as heck here at the moment. - I acknowldge the arguement, and understand it. But the flaw I see is in the tooth differences.
Dragons, Crocodiles etc do change their prey with time. Thats a function of the size of the animal I believe. Their dentition doesn't radically change though neither does their basic form or their method of hunting. Nano-Ts inner ear would have had to rotate about 10 degrees during this period in order to enable it to walk like a Rex without getting vertigo. It'd have to lose it's teeth and grow different types.
It would have to learn how to hunt one type of prey, then another when it grew up. Simply because it had different tools. And if we agree that the type of teeth an animal had was an indication of what it ate, then Nano-T didn't eat the same things as Rex.

Adam Khor

Alvin T. Grey wrote: »

Sorry Adam if this seems a little short, but it's busy as heck here at the moment. - I acknowldge the arguement, and understand it. But the flaw I see is in the tooth differences.
Dragons, Crocodiles etc do change their prey with time. Thats a function of the size of the animal I believe. Their dentition doesn't radically change though neither does their basic form or their method of hunting. Nano-Ts inner ear would have had to rotate about 10 degrees during this period in order to enable it to walk like a Rex without getting vertigo. It'd have to lose it's teeth and grow different types.
It would have to learn how to hunt one type of prey, then another when it grew up. Simply because it had different tools. And if we agree that the type of teeth an animal had was an indication of what it ate, then Nano-T didn't eat the same things as Rex.

Hmm ok I get it... may I ask what the differences between the teeth of T-Rex and Nano-T are? Because I only remember a difference in tooth number. I would expect a juvenile T-Rex to have more slender, blade-like teeth when compared to the adults, though.

Galvasean

I know comparing human dentition to tyrannosaur dentition is akin to apples and oranges, but could tyrannosaurs have had a couple of layers of baby teeth which upon falling out gave way to the adult teeth? A human's baby teeth are very different to the adult set.
There have been dinosaurs found with varying tooth types in their mouths, so changing dentition is not a strictly mammalian trait...

Adam Khor

Galvasean wrote: »

I know comparing human dentition to tyrannosaur dentition is akin to apples and oranges, but could tyrannosaurs have had a couple of layers of baby teeth which upon falling out gave way to the adult teeth? A human's baby teeth are very different to the adult set.
There have been dinosaurs found with varying tooth types in their mouths, so changing dentition is not a strictly mammalian trait...

If I remember correctly, baby crocodiles replace their teeth constantly and even faster than adults, like, once a month for each socket. If dinosaurs were anything like crocodiles (and they were in many ways), it wouldn´t make much sense to have a couple layers of baby teeth that will be replaced within a couple months anyways. I doubt the diet of the animal would change much during that time.
What we need is baby T-Rex fossils found ASAP!

Galvasean

Adam Khor wrote: »

What we need is baby T-Rex fossils found ASAP!

I suppose the best way to prove 100% that Nano T =/= T-rex would be to find a juvenile T. rex that was the same size as, but noticeably different in physiology from Nanotyrannus.

Alvin T. Grey

Adam Khor wrote: »

Hmm ok I get it... may I ask what the differences between the teeth of T-Rex and Nano-T are? Because I only remember a difference in tooth number. I would expect a juvenile T-Rex to have more slender, blade-like teeth when compared to the adults, though.

I'm trying to dig (excuse the pun) up the info on the teeth being somewhat more slender and having a different serration count. The number of teeth is not a good enough indication (I feel) of a distinct difference.

Alvin T. Grey

Galvasean wrote: »

I suppose the best way to prove 100% that Nano T =/= T-rex would be to find a juvenile T. rex that was the same size as, but noticeably different in physiology from Nanotyrannus.

What we need is an indisputable juvenile T-Rex with a complete skull.

Alvin T. Grey

Alvin T. Grey wrote: »

Sorry Adam if this seems a little short, but it's busy as heck here at the moment. - I acknowldge the arguement, and understand it. But the flaw I see is in the tooth differences.
Dragons, Crocodiles etc do change their prey with time. Thats a function of the size of the animal I believe. Their dentition doesn't radically change though neither does their basic form or their method of hunting. Nano-Ts inner ear would have had to rotate about 10 degrees during this period in order to enable it to walk like a Rex without getting vertigo. It'd have to lose it's teeth and grow different types.
It would have to learn how to hunt one type of prey, then another when it grew up. Simply because it had different tools. And if we agree that the type of teeth an animal had was an indication of what it ate, then Nano-T didn't eat the same things as Rex.

Sorry, just to expand on that. Comparing the Komodo Dragon to a T-Rex in terms of behaviour etc is a very large mistake.
The Komodo Islands are exactly that islands. That skews the ecology a whole lot.
Think about it, the landmass just isn't big enough to support more than one top preditor. The ecology isn't veried enough to allow for multiple specialization. With the result that you have (I feel) one good generalist filling multiple roles. But Komodo is the exception, not the rule. In the Certatious period of N. America, we had enough diversity to allow multiple top preditors. Akin to today in Africa we have Lions, Leopards, Crocodiles, Hyeneas etc.

Does that make sense?..

Adam Khor

Alvin T. Grey wrote: »

Sorry, just to expand on that. Comparing the Komodo Dragon to a T-Rex in terms of behaviour etc is a very large mistake.
The Komodo Islands are exactly that islands. That skews the ecology a whole lot.
Think about it, the landmass just isn't big enough to support more than one top preditor. The ecology isn't veried enough to allow for multiple specialization. With the result that you have (I feel) one good generalist filling multiple roles. But Komodo is the exception, not the rule. In the Certatious period of N. America, we had enough diversity to allow multiple top preditors. Akin to today in Africa we have Lions, Leopards, Crocodiles, Hyeneas etc.

Does that make sense?..

I agree, but it's still intriguing that the remains of these hypothetical predators haven`t been found, especially if we consider that T-Rex seems to have been the top cat (bird?) in N. America during the latest Cretaceous and so one would expect it to be relatively rare, with other, smaller predators being much more common. Of course, I know this isn`t a rule (for example, in eastern Africa, lions and hyenas tend to be more abundant locally than leopards, cheetahs and wild dogs). Taking this as an example, I wonder... is this perhaps evidence of T-Rex's living in packs?
Lions and hyenas are formidable predators and since they live in groups, they manage to intimidate other carnivores and limit/reduce their population. Maybe the same happened with T-Rex? Maybe the same happened with Allosaurus in the late Jurassic of N. America, explaining why the larger Allosaurus is more abundant than the smaller Ceratosaurus and other theropods?
Perhaps if T-Rex was a solitary hunter, other predators would be more common at the same time and place! :O What do you guys think?

Alvin T. Grey

Adam Khor wrote: »

I agree, but it's still intriguing that the remains of these hypothetical predators haven`t been found, especially if we consider that T-Rex seems to have been the top cat (bird?) in N. America during the latest Cretaceous and so one would expect it to be relatively rare, with other, smaller predators being much more common. Of course, I know this isn`t a rule (for example, in eastern Africa, lions and hyenas tend to be more abundant locally than leopards, cheetahs and wild dogs). Taking this as an example, I wonder... is this perhaps evidence of T-Rex's living in packs?
Lions and hyenas are formidable predators and since they live in groups, they manage to intimidate other carnivores and limit/reduce their population. Maybe the same happened with T-Rex? Maybe the same happened with Allosaurus in the late Jurassic of N. America, explaining why the larger Allosaurus is more abundant than the smaller Ceratosaurus and other theropods?
Perhaps if T-Rex was a solitary hunter, other predators would be more common at the same time and place! :O What do you guys think?

It is an interesting conundrum to be sure. The top preditor (in this case T-Rex) is distinctly over represented in the record. I feel it may be down to two things;

Firstly, you may be on to something regarding the pack idea. That would explain why T-Rex was able to out compete other species. And if it was a pack , then it is possible that the presence of Rex scent purposly kept out medium to large sized competitors. I feel somehow that smaller carnivors would be present as the Rexs wouldn't see them as a threat to their food source or themselves. Ditto with omnivourous scavengers.

Secondly, there may actually be less Rexs around than we think. - Due to the fact that almost all skeletons are mostly incomplete, a fact that leads to constant reclassification, we may be seeing varied sub species of closly related animals. It's difficult enough to tell from a single femur, a vertebrae, and a few ribs whether you are looking at a Jaguar, or a small Leopard. And that's an extent species. On top of that we actially could count all of the T-Rex finds there have ever been almost without runnning out of fingers. That is what is causing the consternation regarding Nano-T in the first place.

Having said that we are being shown a single instance where an anatomically set charicteristic - the brain, which contains enough difference to reasonably say we are looking at a different species.

Adam Khor

Alvin T. Grey wrote: »

It is an interesting conundrum to be sure. The top preditor (in this case T-Rex) is distinctly over represented in the record. I feel it may be down to two things;

Firstly, you may be on to something regarding the pack idea. That would explain why T-Rex was able to out compete other species. And if it was a pack , then it is possible that the presence of Rex scent purposly kept out medium to large sized competitors. I feel somehow that smaller carnivors would be present as the Rexs wouldn't see them as a threat to their food source or themselves. Ditto with omnivourous scavengers.

Secondly, there may actually be less Rexs around than we think. - Due to the fact that almost all skeletons are mostly incomplete, a fact that leads to constant reclassification, we may be seeing varied sub species of closly related animals. It's difficult enough to tell from a single femur, a vertebrae, and a few ribs whether you are looking at a Jaguar, or a small Leopard. And that's an extent species. On top of that we actially could count all of the T-Rex finds there have ever been almost without runnning out of fingers. That is what is causing the consternation regarding Nano-T in the first place.

Having said that we are being shown a single instance where an anatomically set charicteristic - the brain, which contains enough difference to reasonably say we are looking at a different species.

You have a good point there. I actually remember that Robert Bakker suggested a second species of Tyrannosaurus living in the same time and place; he called it Tyrannosaurus X.
However, the differences to T-Rex are very slight, too much in my opinion for the two beasts to occupy different niches. They are about the same size and have the very same basic design with only a few details setting them apart. IMHO, for two very similar large predators, within the same genus actually, to coexist in the same habitat, prey would have to be extremely abundant. If this was the case we would also find other large-ish and medium-sized predatory dinosaurs that would take advantage of this abundance.
But like we said before such remains haven´t been found, suggesting that those hypothetical predators, if present, were very rare. If this wasn´t because of T-Rex hunting in packs and displacing/supressing other large-ish predators, then it would probably be because of a relative scarcity or low diversity of prey.
I think this makes it unlikely that Tyrannosaurus X actually existed. I'm thinking the differences to T-Rex are probably individual variation.

Of course, what do I know! XD

Galvasean

Fairly certain 'Tyrannosaurus X' and T. rex are just male/females of the same species.

Alvin T. Grey

Ok, lets look at it from the premise that Nano-T is a juvenile T-Rex.

Lets examine what that would mean...

T-Rex is born (possibly alone, actually more likely alone due to the distinct differences in the animal and type of prey). It is adapted to preying on one type of food source. Lets say that is small dinosaurs, your odd mammal (Hi great-great-10X32-grandma..) and maybe some nice crunchy insects.

It begins to mature, the type of prey changes to bigger and bigger animals until it reaches maturity. Right?

Ok,

However two things have to change during that period. Firstly the method of capture and hunting has to change because the type of prey demands that. You can still use ambush techniques, but one must also be ready to chase because smaller prey usually equals faster prey....

Secondly the body form has to change as you mature so that at each stage in the growth you are adapted to match the size and type of prey you hunt. And as we have seen, thats not a trivial matter.

-or-

You can do one of two things if you use the original body type through out your life.

Either you stay a T-Rex, but hunt smaller scaled down prey, using pack tactics with other T-Rexs of the same age, or you are in some way supported by your parents until somehow until you can make a contribution to the hunt.

A good way of telling whether this is true is (and we need to find) to locate a T-Rex nest site.

A small number of eggs means assisted parenting. - A large number of eggs mean likely abandonment.

I know crocodiles lay a lot of eggs, and guard the nest. But what happens after a day or so?

Nomnomnom...burp!

Alvin T. Grey

You got to love Horners take on the matter:

Source:
Cannibalism in Tyrannosaurus rex
Nicholas R. Longrich1*, John R. Horner2, Gregory M. Erickson3, Philip J. Currie4

-snip-
It is usually impossible to refer tooth marks to a particular
species, and here, the traces themselves preserve no distinctive
features other than their size. However, Tyrannosaurus is the only
large theropod known from the Late Maastrichtian of the Western
Interior [14]. The holotype of ‘‘Nanotyrannus lancensis’’ [29] is
immature and displays virtually all the features expected for a
juvenile Tyrannosaurus [14,30], including a skull with a narrow
snout and a broad temporal region, a deep mandible, and an
elongate sagittal crest of the frontal [30]. No adults of
‘‘Nanotyrannus’’ are known, or juveniles of T. rex that clearly differ
from ‘‘Nanotyrannus’’. Thus, ‘‘Nanotyrannus’’ is most parsimoniously
considered a juvenile of Tyrannosaurus. ‘‘Nanotyrannus’’ does have
more maxillary teeth than other specimens of T. rex (fifteen, versus
eleven to twelve for other T. rex) [29,30,31] but given that this
feature is highly variable within species, and even between the left
and right maxillae in a single individual [31], it is insufficient to
warrant the recognition of a separate species. Because there is no
compelling evidence for more than one tyrannosaurid in the
fauna, then by default, the traces described above can be
attributed to Tyrannosaurus.